The Prostate, Lung, Colorectal, and Ovarian Screening Trial (PLCO Trial) is a two-armed randomized trial in which approximately 150,000 individuals will either be screened for the four tumors of interest or not screened. The incidence of the cancers in the two groups will then be compared. The University of Utah will enroll 13,000 subjects on this multi-center trial, of which 10,800 will be evaluated at the GCRC. The remainder will be evaluated at a satellite location in Boise, Idaho. Subjects randomized to the ""screening"" limb will be evaluated annually with chest x-rays, transvaginal ultrasound tests, and sigmoidoscopy and digital rectal exams. Laboratory testing will include monitoring of the CA-125 (a test for ovarian cancer) and the PSA (a test for prostate cancer).